import java.io.UnsupportedEncodingException; public class Base64 {
public static final String DEFAULT_ENCODING = "UTF-8"; /* * The methods of this class are static. Do not instantiate this class. Use * its static methods to get the encoded/decoded results */ public static String encode(byte[] byteData) throws UnsupportedEncodingException {
return encode(byteData, DEFAULT_ENCODING); } public static String encode(byte[] byteData, String encoding) throws UnsupportedEncodingException {
if(byteData == null) {
throw new IllegalArgumentException("byteData cannot be null"); } return new String(_encode(byteData),encoding); } public static byte[] encode(String string) throws UnsupportedEncodingException {
return encode(string, DEFAULT_ENCODING); } public static byte[] encode(String string, String encoding) throws UnsupportedEncodingException {
if(string == null) {
throw new IllegalArgumentException("string cannot be null"); }
return _encode(string.getBytes(encoding));
}
public final static byte[] _encode(byte[] byteData) {
/* If we received a null argument, exit this method. */
if (byteData == null) {
throw new IllegalArgumentException("byteData cannot be null"); }
/* * Declare working variables including an array of bytes that will * contain the encoded data to be returned to the caller. Note that the * encoded array is about 1/3 larger than the input. This is because * every group of 3 bytes is being encoded into 4 bytes. */
int iSrcIdx; // index into source (byteData)
int iDestIdx; // index into destination (byteDest)
// byte[] byteData = (byte[])byteData_in.clone();
// byte[] byteData = byteData_in;
byte[] byteDest = new byte[((byteData.length + 2) / 3) * 4];
/* * Walk through the input array, 24 bits at a time, converting them from * 3 groups of 8 to 4 groups of 6 with two unset bits between. as per * Base64 spec see * http://www.javaworld.com/javaworld/javatips/jw-javatip36-p2.html for * example explanation */
for (iSrcIdx = 0, iDestIdx = 0; iSrcIdx < byteData.length - 2; iSrcIdx += 3) {
byteDest[iDestIdx++] = (byte) ((byteData[iSrcIdx] >>> 2) & 077);
byteDest[iDestIdx++] = (byte) ((byteData[iSrcIdx + 1] >>> 4) & 017 | (byteData[iSrcIdx] << 4) & 077);
byteDest[iDestIdx++] = (byte) ((byteData[iSrcIdx + 2] >>> 6) & 003 | (byteData[iSrcIdx + 1] << 2) & 077);
byteDest[iDestIdx++] = (byte) (byteData[iSrcIdx + 2] & 077);
}
/* * If the number of bytes we received in the input array was not an even * multiple of 3, convert the remaining 1 or 2 bytes. */
if (iSrcIdx < byteData.length) {
byteDest[iDestIdx++] = (byte) ((byteData[iSrcIdx] >>> 2) & 077);
if (iSrcIdx < byteData.length - 1) {
byteDest[iDestIdx++] = (byte) ((byteData[iSrcIdx + 1] >>> 4) & 017 | (byteData[iSrcIdx] << 4) & 077);
byteDest[iDestIdx++] = (byte) ((byteData[iSrcIdx + 1] << 2) & 077);
} else
byteDest[iDestIdx++] = (byte) ((byteData[iSrcIdx] << 4) & 077);
}
/* * Use the encoded data as indexes into the Base64 alphabet. (The Base64 * alphabet is completely documented in RFC 1521.) */
for (iSrcIdx = 0; iSrcIdx < iDestIdx; iSrcIdx++) {
if (byteDest[iSrcIdx] < 26)
byteDest[iSrcIdx] = (byte) (byteDest[iSrcIdx] + 'A');
else if (byteDest[iSrcIdx] < 52)
byteDest[iSrcIdx] = (byte) (byteDest[iSrcIdx] + 'a' - 26);
else if (byteDest[iSrcIdx] < 62)
byteDest[iSrcIdx] = (byte) (byteDest[iSrcIdx] + '0' - 52);
else if (byteDest[iSrcIdx] < 63)
byteDest[iSrcIdx] = '+';
else
byteDest[iSrcIdx] = '/';
}
/* Pad any unused bytes in the destination string with '=' characters. */
for (; iSrcIdx < byteDest.length; iSrcIdx++)
byteDest[iSrcIdx] = '=';
return byteDest;
}
public static String decode(byte[] encoded) throws UnsupportedEncodingException {
return decode(encoded, DEFAULT_ENCODING);
}
public static String decode(byte[] encoded, String encoding) throws UnsupportedEncodingException {
if(encoded == null) {
throw new IllegalArgumentException("encoded cannot be null"); }
return new String(_decode(encoded), encoding);
}
public final static byte[] decode(String encoded) throws UnsupportedEncodingException {
return decode(encoded,DEFAULT_ENCODING);
}
public final static byte[] decode(String encoded, String encoding) throws IllegalArgumentException, UnsupportedEncodingException {
if(null == encoded) {
throw new IllegalArgumentException("encoded cannot be null"); }
return _decode(encoded.getBytes(encoding));
}
public final static byte[] _decode(byte[] byteData) throws IllegalArgumentException {
/* If we received a null argument, exit this method. */
if (byteData == null) {
throw new IllegalArgumentException("byteData cannot be null"); }
/* * Declare working variables including an array of bytes that will * contain the decoded data to be returned to the caller. Note that the * decoded array is about 3/4 smaller than the input. This is because * every group of 4 bytes is being encoded into 3 bytes. */
int iSrcIdx; // index into source (byteData)
int reviSrcIdx; // index from end of the src array (byteData)
int iDestIdx; // index into destination (byteDest)
byte[] byteTemp = new byte[byteData.length];
/* * remove any '=' chars from the end of the byteData they would have * been padding to make it up to groups of 4 bytes note that I don't * need to remove it just make sure that when progressing throug array * we don't go past reviSrcIdx ;-) */
for (reviSrcIdx = byteData.length; reviSrcIdx -1 > 0 && byteData[reviSrcIdx -1] == '='; reviSrcIdx--) {
; // do nothing. I'm just interested in value of reviSrcIdx
}
/* sanity check */
if (reviSrcIdx -1 == 0) {
return null; /* ie all padding */ }
/* * Set byteDest, this is smaller than byteData due to 4 -> 3 byte munge. * Note that this is an integer division! This fact is used in the logic * l8r. to make sure we don't fall out of the array and create an * OutOfBoundsException and also in handling the remainder */
byte byteDest[] = new byte[((reviSrcIdx * 3) / 4)];
/* * Convert from Base64 alphabet to encoded data (The Base64 alphabet is * completely documented in RFC 1521.) The order of the testing is * important as I use the '<' operator which looks at the hex value of * these ASCII chars. So convert from the smallest up * * do all of this in a new array so as not to edit the original input */
for (iSrcIdx = 0; iSrcIdx < reviSrcIdx; iSrcIdx++) {
if (byteData[iSrcIdx] == '+')
byteTemp[iSrcIdx] = 62;
else if (byteData[iSrcIdx] == '/')
byteTemp[iSrcIdx] = 63;
else if (byteData[iSrcIdx] < '0' + 10)
byteTemp[iSrcIdx] = (byte) (byteData[iSrcIdx] + 52 - '0');
else if (byteData[iSrcIdx] < ('A' + 26))
byteTemp[iSrcIdx] = (byte) (byteData[iSrcIdx] - 'A');
else if (byteData[iSrcIdx] < 'a' + 26)
byteTemp[iSrcIdx] = (byte) (byteData[iSrcIdx] + 26 - 'a');
}
/* * 4bytes -> 3bytes munge Walk through the input array, 32 bits at a * time, converting them from 4 groups of 6 to 3 groups of 8 removing * the two unset most significant bits of each sorce byte as this was * filler, as per Base64 spec. stop before potential buffer overun on * byteDest, remember that byteDest is 3/4 (integer division) the size * of input and won't necessary divide exactly (ie iDestIdx must be < * (integer div byteDest.length / 3)*3 see * http://www.javaworld.com/javaworld/javatips/jw-javatip36-p2.html for * example */
for (iSrcIdx = 0, iDestIdx = 0; iSrcIdx < reviSrcIdx
&& iDestIdx < ((byteDest.length / 3) * 3); iSrcIdx += 4) {
byteDest[iDestIdx++] = (byte) ((byteTemp[iSrcIdx] << 2) & 0xFC | (byteTemp[iSrcIdx + 1] >>> 4) & 0x03);
byteDest[iDestIdx++] = (byte) ((byteTemp[iSrcIdx + 1] << 4) & 0xF0 | (byteTemp[iSrcIdx + 2] >>> 2) & 0x0F);
byteDest[iDestIdx++] = (byte) ((byteTemp[iSrcIdx + 2] << 6) & 0xC0 | byteTemp[iSrcIdx + 3] & 0x3F);
}
/* * tidy up any remainders if iDestIdx >= ((byteDest.length / 3)*3) but * iSrcIdx < reviSrcIdx then we have at most 2 extra destination bytes * to fill and posiblr 3 input bytes yet to process */
if (iSrcIdx < reviSrcIdx) {
if (iSrcIdx < reviSrcIdx - 2) {
// "3 input bytes left"
byteDest[iDestIdx++] = (byte) ((byteTemp[iSrcIdx] << 2) & 0xFC | (byteTemp[iSrcIdx + 1] >>> 4) & 0x03);
byteDest[iDestIdx++] = (byte) ((byteTemp[iSrcIdx + 1] << 4) & 0xF0 | (byteTemp[iSrcIdx + 2] >>> 2) & 0x0F);
} else if (iSrcIdx < reviSrcIdx - 1) {
// "2 input bytes left"
byteDest[iDestIdx++] = (byte) ((byteTemp[iSrcIdx] << 2) & 0xFC | (byteTemp[iSrcIdx + 1] >>> 4) & 0x03);
}
/* * wont have just one input byte left (unless input wasn't base64 * encoded ) due to the for loop steps and array sizes, after "=" * pad removed, but for compleatness */
else {
throw new IllegalArgumentException("Warning: 1 input bytes left to process. This was not Base64 input");
}
}
return byteDest;
}
}